[PATCH] md: close a small race in md thread deregistration
[sfrench/cifs-2.6.git] / drivers / md / md.c
index aa72c88a024f7ef06f4c32263497a379c0bd7094..44a164965546c3a57d60c2a9d90d9dce2c4962c7 100644 (file)
@@ -2840,16 +2840,6 @@ mdk_thread_t *md_register_thread(void (*run) (mddev_t *), mddev_t *mddev,
        return thread;
 }
 
-static void md_interrupt_thread(mdk_thread_t *thread)
-{
-       if (!thread->tsk) {
-               MD_BUG();
-               return;
-       }
-       dprintk("interrupting MD-thread pid %d\n", thread->tsk->pid);
-       send_sig(SIGKILL, thread->tsk, 1);
-}
-
 void md_unregister_thread(mdk_thread_t *thread)
 {
        struct completion event;
@@ -2857,9 +2847,15 @@ void md_unregister_thread(mdk_thread_t *thread)
        init_completion(&event);
 
        thread->event = &event;
+
+       /* As soon as ->run is set to NULL, the task could disappear,
+        * so we need to hold tasklist_lock until we have sent the signal
+        */
+       dprintk("interrupting MD-thread pid %d\n", thread->tsk->pid);
+       read_lock(&tasklist_lock);
        thread->run = NULL;
-       thread->name = NULL;
-       md_interrupt_thread(thread);
+       send_sig(SIGKILL, thread->tsk, 1);
+       read_unlock(&tasklist_lock);
        wait_for_completion(&event);
        kfree(thread);
 }